Machine for grinding facets in lenses



Dec. 3, 1957 E. M. ADAMS 2,314,916

MACHINE FOR GRINDING FACETS IN LENSES Filed Dec. 5, 1955 2 Sheets-Sheetl INVENTOR. EDWIN M. ADHMS Dec. 957 E. M. ADAMS 2,314,916

MACHINE FOR GRINDING FACETS IN LENSES Filed Dec. 5, 1955 2 Sheets-Sheet2 INVENTOR. EDWIN. M FTDHMS BY wdh'axmdamscfinpadufldmmfllh 'm H T TOR NE VS United States Patent MACHINE FOR GRINDING FACETS IN LENsEs Edwin M.Adams, Minneapolis, Minn., assignor to Precisioh-Cosmet Company, Inc.,Minneapolis, Minn., a corporation of Minnesota Application December 5,1955, Serial No. 551,054

7 Claims. (Cl. 5198) This invention relates to machines for formingfacets in'the edges of lenses and more specifically relates to improvedmechanism for controlling the positioning of and spacing between suchfacets.

An' object of my invention is to provide a new and improved machine ofsimple and inexpensive construction and operation for readily and easilyforming facets in the peripheral edge portions of lenses.

Another object of my invention is the provision in a facet-grindingmachine of improved mechanism for incrementally rotating a lens througha predetermined arc in each cycle of operation during which the lens isshifted toward the grinding tool, is ground and is again shifted. awayfrom the grinding tool.

A further object of my invention is to provide in a lens-grindingmachine for forming facets in the lens edge, novel mechanism forrotating and selectively controlling the are of rotation of the lens andthe spacing between facets formed by oscillation of the lens toward andaway from the grinding-tool.

A still further object of my invention is to provide novel and improvedmanually controllable apparatus for releasably gripping the lens whichmust be securely held under strong tension during the servicing of theedge portions thereof.

These and other objects and advantages of my invention will more fullyappear from the following description made in connection with theaccompanying drawings wherein like reference characters refer to similarparts throughout the sever-a1 views and in which:

Fig. 1 is a top plan view of the machine including the invention;

Fig. 2 is a rear elevation view of the machine shown in Fig. 1;

Fig. 3 is a detail view of a portion of the machine and being takensubstantially on a plane as indicated at 3-3 in Fig. 2 andhavingportions of the background mechanism removed for clarity and simplicity;

Fig. 4 is a detail section view of a portion of the machine with certainportions thereof broken away for simplicity and clarity and takensubstantially on a horizontal plane as indicated at 4-4 of Fig. 2;

Fig. 5 is a detail section view with portions of the mechanism brokenaway and being taken substantially on a vertical plane as indicated at5-5 of Fig. 1;

Fig. 6 is a detail section view taken on a substantially vertical planeas indicated at 6-6 of Fig. 1; and

Fig. 7 is a plan view of one of the cut spacing wheels with a lenssuperimposed thereon to show the relation between the spacing of theteeth on the wheel and the spacing of facetson the edge of anirregularly shaped lens.

One form of the invention is shown in the figures and described herein.The machine includes a base plate or frame indicated in general bynumeral 10. A source of rotary. power comprising motor 11 is affixed onframe adjacent the rear portion thereof. A pair of upright standards 12are affixed as by bolts 13 to the base 10 2,814,916 Patented Dec. 3,1957 and have a rotary shaft 14 journal'led in the upper portionsthereof. Shaft 14 is keyed to a grinding device or tool 15 for rotationtherewith. Shaft 14 has a pulley l6 fixed thereto as by set screws 17and is connected to the rotary pindle 18 having a pulley 19 securedthereto by means of belt 20. A water receptacle 21 is also carried onstandards 12 and has an outlet 22 extending into proximity with theperipheral surface of the rotary grinding tool 15.

Means are provided on the machine for holding a lens L in edge-grindingrelation with respect to grinding wheel 15 and for moving the lenstoward and away from the wheel 15. In the form shown, such meanscomprise a tubular handle 23 having a mounting portion 24 which isswingably connected as by pivot 25 to a slide mounting 26. Slidemounting 26 is provided with an opening 27 therethrough through whichextends an elongated mounting element or flat bar 28 which is pivotallysecured to frame 10 by a bolt 29 and wing nut 30 for swinging movementin a horizontal plane adjacent frame 10. The wing nut 30 may betightened and loosened to permit the bar 28 to be substantially lockedin position on frame 10 and to permit movement thereof about bolt 29.Slide mounting 26 has a manually operable set screw 31 threadablycarried therein and disposed for engaging the bar 28 for locking slidemounting 26 in a desired position along the length of bar 28.

A lens holder indicated in general by numeral 32 is carried by handle 23and the mounting 24 thereof for oscillatory movement with the handle 23toward and away from the grinding tool 15. In the form shown, the lensholder includes a pair of jaws 33 and 34 which may be provided withsuitable padding for engaging the lens surfaces and which are rotatableabout an axis extending transversely of and through the lens. Jaw 33 isfixed to a supporting post 35 which is journalled in handle mounting 24.Jaw 34 is journalled in a supporting arm or element 36 which extendstransversely of handle 23. Supporting arm 36 is affixed to a sleevemember 37 which is slidably mounted in the hollow interior of handle 23.Support arm 36 is also provided with an annular flange 38 which extendsoutwardly around sleeve 37 and is coaxially disposed relative to handle23. A guide rod 39 is 'threadably aflixed at 40 to handle 23 in theinterior thereof and has a resiliently yieldable compression spring 41disposed therearound. The upper end portion of spring 41 engages andbears against suitable stop means such as nut 42 which is threadablysecured on the upper end portion of rod 39. The lower end portion ofspring 41 engages and bears against the inwardly extending end 37a atthe bottom portion of sleeve 37. A closure cap 43 is carried on theupper portion of sleeve 37 for closing the same.

The present invention includes improved means for shifting jaws 33 and34 away from each other. Such means include an actuating element 44which has a yoke 45 formed on the inner end thereof which extends aroundopposite sides of sleeve 37. Yoke 45 bears against the flange 38 and theupper annular edge of handle 23. A pin 46 extends through suitablealigned apertures provided in flange 38, yoke 45 and an appendageportion 23a of handle 23 for securing actuating element 44 in operativeposition. The outer end portion 47 of actuating element 44 extendsgenerally outwardly from handle 23 and away from the jaws 33 and 34, andthe outer portion 47 is flattened and smoothly rounded at the edges sothat it may be comfortably engaged and operated by the palm of a personshand.

The present invention includes drive means for incrementally rotatinglens L in synchronism with the oscillatory forward and rearward movementthereof toward and away from grinding wheel 15. Such drive means arealso adjustable for permitting the lens to be selectively rotatedthrough a desired and predetermined are each time the same is shiftedfor forming differently spaced facets in the lens edge. Such drive meansinclude a driven mechanism which, in the form shown, comprises a pair ofrotary ratchet or driven elements 48 and 49 which are coaxiallyinterconnected and atfixed to the rotary supporting post 35. The ratchetelements 48 and 49 are substantially circular and are provided withteeth 50 and 51 respectively which are of different sizes and which arespaced differently around the peripheral edge portions of the ratchetelements. In the form shown, the teeth 50 are spaced farther apart thanare teeth 51.

Such drive means also include driving mechanism which comprises, in theform shown, a pair of pawls or driving elements 52 and 53. Pawls 52 and53 are connected through mounting member 54 and frame 10 to the grindingdevice 15 for relative oscillatory movement with respect to the drivenor ratchet elements 48 and 49 and toward and away from the grindingdevice 15. Pawls 52 and 53 are swingably mounted for movement about asubstantially vertical axis on pin 55 which is fixed in mounting member54. A pair of coil springs 56 and 57 are carried on pin 55 andrespectively bear against pawls 52 and 53 for urging the same intoengagement with the teeth of ratchet wheels 48 and 49 respectively.Mounting member 54 is swingably mounted on pivot 25. Means are alsoprovided for restricting the swinging movement of mounting member 54with respect to frame 10 and in the form shown, such means include apair of braking washers 58 which are also carried on pivot 25 and whichengage the mounting 54. Brake washers 58 may be constructed of anysuitable material such as an asbestos fabric with metallic threadsinterwoven therein. The braking washers 58 are urged into brakingengagement with mounting member 54 by washers 59, retaining element 60and a nut 61 which is threadably secured to the end of pivot 25.

Means are also provided on mounting member 54 for controlling pawls 52and 53 and for selectively causing the same to engage and disengagetheir respective ratchet elements 48 and 49. Such means is best seen inFigs. 4 and and includes a control 62 which is rotatably mounted onscrew 63 which is threadably affixed to mounting 54. The control 62 isalso slidable on screw 63 toward and away from mounting 54, and control62 is normally resiilently urged inwardly toward mounting member 54 bycompression spring 64 which, at one end bears against the inner portionof control 62 and at the outer portion bears against the head of screw63. A pin 65 is affixed to control 62 and is positioned to extendthrough either of the apertures 66 and 67 formed in mounting member 54adjacent the pawls 52 and 53 respectively. As seen in Fig. 4, pin 65engages pawl 52 when inserted through aperture 66 for shifting pawl 52out of engagement with the teeth of the ratchet element 48. Similarly,when pin 65 is inserted through aperture 67, pawl 53 is shifted therebyout of engagement with the teeth of ratchet wheel 49.

Means are also provided for controllably limiting the relativeoscillatory movement between the driving mechanism and the drivenmechanism, that is, between pawls 52 and 53 and ratchet wheels 48 and49. In the form shown, a pair of stop arms or abutments 68 and 69 aredisposed in spaced relation relative to each other and in spacedrelation with the post 35 which is affixed to ratchets 48 and 49. In theform shown, arms 68 and 69 are formed integrally of mounting member 54.Arms 68 and 69 along with the mounting portion 24 and mounting member54, which is mounted on pivot 25 independently of mounting portion 24,provide a yieldable connection between the shiftable lens holder 32 andthe driving mechanism which is embodied in the present form of theinvention by pawls 52 and 53.

Means are also provided for adjusting the limits of relative oscillatorymovement between the driving elements or pawls 52 and 53 and the drivenelements or ratchets 48 and 49. In the form shown, such means include astop element 70 which is secured by rod 71 to the control 62 for rotaryand reciprocating movement therewith. Stop element 70 is positionedinwardly of arm 68 and in engagement with abutment 72 which is affixedto arm 68, when the control 62 is positioned so that pin 65 is insertedthrough aperture 66 for engaging pawl 52. Stop element 70 may be shiftedlongitudinally and swung with corresponding shifting of control 62around abutruent 72 and into the dotted position thereof shown in Fig. 3to permit full and unobstructed movement of post 35 with respect to arms68 and 69.

A supporting device 73 carried by bracket 74 is mounted on the standard12 for supporting the edge of the lens L as the same is shifted intoengagement with the rotary grinding wheel 15.

It will be noted in Fig. 7 that in order to make the facets formed inthe lens L of regular size, the teeth formed in the ratchet element 48must be irregularly shaped because the ratchet element 48 is circular inshape and whereas the lens L has an irregular peripheral outline. Theratchet teeth in ratchet element 49 are similarly irregularly spaced soas to provide for the regular spacing of facts formed in the peripheraledges.

Operation In the operation of the lens-grinding machine, the bandle 23will be manually gripped by the ends of the person's fingers and thepalm of his hand will be placed upon the upper side of actuating member44. Although the spring 41 is exceedingly strong, the actuating element44 may be fulcrumed against the upper portion of handle 23 and theflange 38 so as shift jaw 34 away from jaw 33. The lens L will then beplaced between the jaws 33 and 34 in the manner shown in Fig. 6 so thatthe axis of rotation of the holder 32 will extend transversely of andthrough the lens. The actuating element 44 will then be released tocause the jaws to securely grip the lens.

The operator of the lens-grinding machine may then shift his gripdirectly onto handle 23 to permit convenient and easy operation thereof.If it is desired to grind relatively small facets in the lens edges, thecontrol 62 will be placed in the condition shown in full lines in thedrawings. The stop element 70 is thereby placed between the abutment 72and the post 35 for limiting the relative oscillatory movement betweenthe driven or ratchet means and the driving or pawl means, and inaddition pin 65 is inserted through the upper aperture 66 intoengagement with pawl 52 to swing the forward engaging portion thereofout of engagement with the ratchet element 48. Pawl 53 will remain inengagement with the lower ratchet wheel 49 for driving the same anddetermining the incremental arcs through which lens L will be rotated asthe same is shifted toward and away from the grinding device 15.

It may be desirable to move the lens-holding device toward or away fromwheel 15 by moving slide mounting 26 along the flat bar 28 and it alsomay be desirable to swing the holder about the bolt 29 so as to causethe lens when oscillated forwardly about pivot 25 to engage the grindingwheel 15 in a particular manner so as to form facets of desiredcontours. After the fiat bar 28 and the slide mounting 26 have beenfixed in position, handle 23 may be oscillated about pivot 25 toward andaway from wheel 15 and thereby similarly shift lens L toward grindingwheel 15, into engagement therewith, and away from wheel 15. As handle23 is ocillated forwardly from the position shown, the lens L andratchet 49 will be moved forwardly, and during the first incrementalforward movement thereof, the mounting member 54 will remain in astationary position because of the action of the braking washers 58. Theratchet element 49 is shifted forwardly relative to pawl 53 whichremains substantially stationary and the pawl 53 will swing slightlyabout its pivot 55 and will be urged into engagement with the next tooth51 disposed clockwise from the tooth previously engaged. As the handle23 continues to be moved forwardly, arm 69 of mounting frame 54 will beengaged by post 35 so as to cause cooperative movement about pivot 25 ofthe ratchet 49 and pawl 53 and there will be no more relative movementtherebetween during the forward motion of handle 23. Lens L willsubstantially engage the grinding wheel 15 and a facet will be formed inthe edge of the lens. When the facet has been formed, handle 23 will beagain swung rearwardly about pivot 25 and because of the action of thebraking washer 58 the mounting frame 54 will at least momentarily remainstationary, thereby causing a relative movement between the ratchetelement 49 and pawl 53 about pivot 25. Because pawl 53 is engaged withone of the teeth 51 of ratchet 49, the relative oscillatory movementtherebetween will be transformed into a rotary movement of ratchet 49about the axis of rotation thereof to cause the lens holder 32 to rotatethrough an increment proportional to the spacing of one of the teeth 51of ratchet 49. The rotation of ratchet 49 and holder 32 is limited bythe limits of oscil latory movement permissible between ratchet 49 andpawl 53 and this is defined by the spacing between stop element 70 andarm 69. When the post 35 engages stop element 70 the mounting frame 54and pawl 53 will swing, along with handle 23 and ratchet 49, about pivot25, rearwardly away from grinding wheel 15. The lens L will have thenbeen rotated through an arc and will be properly positioned forengagement with the grinding wheel 15 again so that a properlypositioned facet away may again be formed therein adjacent thepreviously formed facet.

The described cycle of operation will be repeated and the handle 23 willbe moved forwardly and the pawl 53 will move to the next adjacent tooth52 in ratchet 49.

Handle 23 will be oscillated forwardly and rearwardly about pivot 25 tocause the lens L to engage the grinding wheel 15 a multiplicity of timesuntil facets have been formed all the way around the peripheral edge ofthe lens. Depending upon the design of the lens desired, the lens maythereafter be turned over so as to form facets adjacent the bottomsurface in the peripheral edge thereof.

If it is desired to form facets of a somewhat larger size in the lensedges, the control 62 will be pulled outwardly from mounting frame 54 soas to retract pin 65 from aperture 66 and so as to retract stop element70 away from abutment 72. The control 62 will be rotated so as to insertpin 65 into aperture 67 and so as to swing the stop element 70 into thedotted position thereof shown in Fig. 3. When the pin 65 is removed fromaperture 66, pawl 52 will be resiliently urged by spring 56 into drivingengagement with the teeth 50 of ratchet 48. The pawl 52 and the spacingbetween teeth 50 will thereupon control and be determinant of thespacing between the facets formed in the lens L. When pin 66 is insertedinto aperture 67, pawl 53 will be swung around pivot 55 out ofengagement with the ratchet 49, and in addition the stop element 70 isremoved from between abutment 72 and post 35. The operation of themechanism is substantially similar to that already described with theexception that there will be slightly greater relative oscillatorymovement between ratchet 48 and pawl 52 than was permissible betweenratchet 49 and pawl 53. This is necessary to permit the relativelygreater shifting due to the larger teeth 50.

It will be seen that I have provided an improved and novel mechanism ina lens facet-grinding machine for controllably producing relativerotation between the lens to be ground and the grinding device each timethe lens is successively brought to bear against and shifted away fromthe grinding device and forming facets of desired size and spacing inthe lens.

It should also be noted that I have provided novel and improvedmechanism for readily and easily shifting the lens-gripping jaws awayfrom each other to facilitate the insertion of a lens therebetween eventhough the spring pressure on the jaws may be very considerable, andwherein said mechanism is provided with an actuating element disposed sothat substantial force may be applied thereupon with the palm of thehand and so that it will normally be out of the way when thelens-grinding ma chine is used in its conventional manner.

It will, of course, be understood that various changes may be made inthe form, details, arrangement and proportions of the parts withoutdeparting from the scope of my invention which consists of the mattershown and described herein and set forth in the appended claims.

I claim:

1. Apparatus for grinding facets in lens edges, comprising a frame, agrinding device mounted on said frame, a releasable lens-holding deviceshiitably mounted on said frame for oscillatory movement toward and awayfrom said grinding device, said holding device being constructed andarranged for holding a lens in edge-grinding relation relative to saidgrinding device, said lens-holding device also being rotatable about anaxis extending transversely of and through the lens, a rotary ratchetelement secured to said holding device for movement therewith. amounting member mounted on said frame adjacent said ratchet element forrestricted oscillatory movement toward and away from said grindingdevice, a pawl movably mounted on said mounting member and engaging saidratchet element in driving relation, said pawl and said ratchet elementbeing relatively movable for power transmission therebetween, andcooperatively abutting stop elements on said holding device and saidmounting member and limiting the magnitude of movement therebetween forlimiting rotative movement of said pawl and ratchet element, whereby toprogressively and incrementally rotate the lens as the same is shiftedtoward and away from said grinding device and thereby form spaced facetsin the peripheral edge thereof.

2. Apparatus for grinding facets in lens edges, comprising a frame, agrinding device, a lens-holding device, said devices mounted on saidframe for relative oscillatory movement toward and away from each otherinto and out of lens-grinding relation, said holding device beingarranged to position the lens in edge-grinding relation relative to thegrinding device, said devices also being rotatable relative to eachother about an axis extending transversely of and through the lens,adjustable drive means operatively connected with said devices andincluding a rotary driven mechanism and a driving mechanism eachdrivably engaging the other and each drivably connected with arespective device to be operated with relative oscillatory movement ofsaid devices, said mechanisms being movable relative to each other forpower transmission therebetween and said mechanisms being constructedand arranged for producing relative rotation of said devices whenoperated by relative oscillatory movement of said devices, adjustablemovementlimiting means connected with said frame and being operativelyconnected with said driven mechanism and said driving mechanism, saidlimiting means being constructed and arranged for selectively andadjustably limiting the magnitude of relative movement of said drivenmechanism and said driving mechanism, whereby to controllably vary theincremental relative rotation of said devices as the same are shiftedtoward and away from each other and thereby vary the spacing of facetsformed in the lens edge.

3. Apparatus for grinding facets in lens edges, comprising a frame, agrinding device mounted on said frame, a lens-holding device mounted onsaid frame, one of said devices being shiftable toward and away from theother of said devices, said holding device being constructed andarranged to hold the lens in edge-grinding relation relative to thegrinding device, one of said devices being rotatable relative to theother of said devices about an axis extending transversely of andthrough the lens, a rotary driven mechanism drivably connected with saidrotatable device for rotating the same, driving mechanism drivablyconnected with said rotary driven mechanism for rotating the same, ayieldable connection between said shiftable device and said drivingmechanism, adjustable movementlimiting means operatively connected withsaid driving mechanism and with said driven mechanism and beingconstructed and arranged for adjustably and selectively limiting themagnitude of relative movement of said driving mechanism and said drivenmechanism, whereby to adjustably vary the incremental rotary movement ofsaid rotatable device and thereby vary the spacing of facets formed inthe lens edge.

4. Apparatus for grinding facets in lens edges, comprising a frame, agrinding tool mounted on said frame, a lens holder shiftably mounted onsaid frame for oscillatory movement toward and away from the grindingtool, said holder being arranged for positioning the lens inedge-grinding relation relative to said grinding tool, said holder alsobeing rotatable on an axis extending transversely of and through thelens, a rotary driven mechanism drivably connected with said lens holderand being shiftably mounted for oscillatory movement therewith, drivingmechanism shiftably mounted on said frame for movement toward and awayfrom the grinding tool and being shiftable relative to said drivenmechanism, said driving mechanism drivably engaging the driven mechanismand being constructed and arranged for rotating the same when shiftedrelative thereto, adjustable stop means operatively connected betweensaid driven mechanism and said driving mechanism and being constructedand arranged for adjustably limiting the magnitude of relative movementbetween said driven mechanism and said driving mechanism, whereby toincrementally rotate said holder and the lens as the same are shiftedtoward and away from the grinding tool for spacing the facets formed atdesirable intervals in the lens edge.

5. Apparatus for grinding facets in lens edges, comprising a frame, agrinding tool mounted on said frame, a lens holder shiftably mounted onsaid frame for oscillatory movement toward and away from said grindingtool, said lens holder being arranged to position the lens inedge-grinding relation relative to the grinding tool, said lens holderalso being rotatable about an axis extending transversely of and throughthe lens, at least a pair of rotary and substantially circular driveelements drivably connected with the lens holder and being movablycarried by said frame for oscillatory movement with the lens holder,said drive elements having spaced driving teeth on the periphery, thespacing between said teeth on one of said drive elements being differentthan the spacing between the teeth on the other of said drive elements,a mounting member adjustably mounted on said frame for oscillatorymovement relative to said drive elements and toward and away from thegrinding tool, pawl means movably mounted on said mounting member andbeing constructed and arranged for selective and interchangeable drivingengagement with said drive elements and the differently spaced teeththereof, stop means operalively connected between said drive elementsand said pawl means and being constructed and arranged for restrictingthe magnitude of relative movement thereof, whereby to selectively varythe incremental arc of rotation of said holder and the lens when thesame are shifted toward and away from the grinding tool and therebyselectively vary the spacing of facets formed in the lens edge.

6. Apparatus for grinding facets in lens edges, comprising a frame, agrinding tool mounted on said frame, a lens holder shiftably mounted onsaid frame for oscillatory movement toward and away from said grindingtool, said lens holder being arranged to position the lens inedge-grinding relation relative to the grinding tool, said lens holderalso being rotatable about an axis extending transversely of and throughthe lens, at least a pair of rotary and substantially circular driveelements drivably connected with the lens holder and being movablycarried by said frame for oscillatory movement with the lens holder,said drive elements having spaced driving teeth on the peripherythereof, the spacing between said teeth on one of said drive elementsbeing different than the spacing between the teeth on the other of saiddrive elements, a mounting member adjustably mounted on said frame foroscillatory movement relative to said drive elements and toward and awayfrom the grinding tool, adjustable pawl means movably mounted on saidmounting member and being constructed and arranged for selective andinterchangeable driving engagement with said drive elements and thedifferently spaced teeth thereof, adjustable stop means operativelyconnected between said drive elements and said pawl means and beingconstructed and arranged for limiting and varying the magnitude ofrelative movement thereof, and a control connected with said stop meansand with said pawl means for simultaneously adjusting the same to changethe relative movement between said pawl means and said drive elementswhen said pawl means change from driving engagement with one drivingelement to driving engagement with the other of said drive elements.

7. Apparatus for grinding facets in lens edges, comprising a frame, agrinding tool mounted on said frame, a lens holder shiftably mounted onsaid frame for oscillatory movement toward and away from the grindingtoo], said lens holder being arranged to position the lens inedge-grinding relation relative to the grinding device and said lensholder also being rotatable about an axis extending transversely of andthrough the lens, at least a pair of rotary and substantially circulardrive elements drivably connected with said lens holder and beingmovably carried on said frame for oscillatory movement with the holdertoward and away from the grinding tool, said drive elements havingspaced driving teeth on the periphery thereof, said teeth on one of saiddrive elements being spaced differently than the teeth on the other ofsaid driving elements. a mounting member shiftably mounted on said framefor oscillatory movement relative to said drive elements and toward andaway from the grinding tool, a pair of movable ratcheting pawls eachmounted on said mounting member adjacent a respective drive element formovement toward and away therefrom, shiftable control means mounted onsaid mounting member and being operatively connected with said pawls forselectively and interchangeably moving the same into and out of drivingrelation with the respective driving elements, and stop meansoperatively connected between said pawls and said drive elements forlimiting relative oscillatory movement theerof, whereby to selectivelyvary the spacing of facets formed in the lens edge.

References Cited in the file of this patent UNITED STATES PATENTS

